Add tests for the Display operation of the mac notification bridge.

chrome/browser/notifications/notification_platform_bridge_mac.h

Index: chrome/browser/notifications/notification_platform_bridge_mac.h
diff --git a/chrome/browser/notifications/notification_platform_bridge_mac.h b/chrome/browser/notifications/notification_platform_bridge_mac.h
index b48f1896242ed15cd148a6a7da6496afe8c9acb1..31bfb1d548927f05af2d1a2daa4c44a240a01017 100644
--- a/chrome/browser/notifications/notification_platform_bridge_mac.h
+++ b/chrome/browser/notifications/notification_platform_bridge_mac.h
@@ -9,6 +9,7 @@
 #include <string>
 
 #include "base/compiler_specific.h"
+#include "base/gtest_prod_util.h"
 #include "base/mac/scoped_nsobject.h"
 #include "base/macros.h"
 #include "chrome/browser/notifications/notification_common.h"
@@ -46,6 +47,16 @@ class NotificationPlatformBridgeMac : public NotificationPlatformBridge {
   static bool VerifyNotificationData(NSDictionary* response) WARN_UNUSED_RESULT;
 
  private:
+  FRIEND_TEST_ALL_PREFIXES(NotificationPlatformBridgeMacTest,
+                           TestDisplayNoButtons);
+  FRIEND_TEST_ALL_PREFIXES(NotificationPlatformBridgeMacTest,
+                           TestDisplayOneButton);
+  FRIEND_TEST_ALL_PREFIXES(NotificationPlatformBridgeMacTest, TestClose);
+
+  // Used directly in tests.
+  NotificationPlatformBridgeMac(NSUserNotificationCenter* notification_center,
+                                bool set_delegate);
+
   // Cocoa class that receives callbacks from the NSUserNotificationCenter.
   base::scoped_nsobject<NotificationCenterDelegate> delegate_;